1. Field of the Invention
The present invention relates to a chain transmission including a chain having a plurality of plates and a chain guide mechanism that guides the chain in sliding contact therewith.
2. Description of the Related Art
Conventionally known timing chain systems for car engines (see, for example, Japanese Patent Application Laid-open No. 2007-107583) include, for example, a chain transmission including a chain having a plurality of plates and a chain guide mechanism.
This known timing chain system is made up of sprockets mounted to a crankshaft and a camshaft inside an engine room, a chain passing over the sprockets, a fixed guide fixed to the engine block for guiding the chain, a pivot guide pivotally attached to the engine block for guiding the chain, and a tensioner that presses the pivot guide to give an appropriate tension to the chain.
In the chain described in Japanese Patent Application Laid-open No. 2007-107583, in order to reduce the contact area between the chain and the pivot/fixed guides to reduce the friction loss in the transmission of power, outer plates have a smaller backside height than inner plates so that only the inner plates contact the pivot guide and fixed guide when the chain runs, i.e., the number of plates that contact the pivot/fixed guides is reduced.
With a fewer number of plates in contact with the pivot/fixed guides as in the chain described in Japanese Patent Application Laid-open No. 2007-107583, slide resistance of the running chain is reduced because the contact area between the chain and the pivot/fixed guides is reduced. On the other hand, the contact pressure per area is increased. There was thus a problem in that, in some areas of contact between the guides and plates, where the radius of curvature of the guides is small, the contact pressure therebetween could become excessive, and this results in a reduction in durability of the guides and plates.